A brake system of the general type under consideration is described in DE 10336611 A1. This known brake system is equipped not only with a service brake but also with a parking brake, in order that the vehicle can be parked with the brake engaged. Such a parking brake is also known as a handbrake.
Parking brakes are usually provided with spring-actuated brake cylinders, in which an actuator spring engages the brake, so that the vehicle is braked or held immobile. This parking brake is released by pressurizing the spring-actuated brake cylinders with compressed air, so that the actuator spring is compressed and, thus, the parking brake is released.
Such spring-actuated brake cylinders are usually designed as combination service-brake and spring-actuated brake cylinders. They therefore have a spring-actuator part and a service-brake part. Service braking is conventionally actuated via a brake pedal.
The compressed-air supply of the spring-actuator part for releasing the parking brake is achieved by means of an air-flow-boosting valve device, especially a relay valve. At its output the air-flow-boosting valve device delivers the same pressure that is present at its control input, but with a boosted air flow, which is drawn from a compressed-air reservoir tank.
The control input of the air-flow-boosting valve device is supplied with the control pressure via at least one control valve. This control valve is designed as an electrically actuatable control valve, wherein the switched condition of this valve is determined by an electrical control device. The control device, in turn, is electrically connected to an actuating device for actuation of the parking brake. This actuating device may be actuated by the driver of the vehicle. The driver is able to release or engage the parking brake by means of this actuating device.
In the brake system described in DE 10336611 A1, the control device is integrated in a parking-brake module, as is a valve module, in which the valves of the parking brake are structurally integrated. As a result, a compact parking-brake module is realized that can be integrated easily into existing air-brake systems. However, this integration requires special housing parts and modules that have to be specially developed.